Wirt sells one magic item at a time, usually only a mildly-powerful one, and he’ll only let you look at it for an advance fee. His prices are way too high, and he justifies this by ranting about some sort of get-rich-and-powerful plan. Most players just want to see him dead1.

1Spoiler Alert (read at your own risk): In Diablo II, when you revisit Tristram to rescue Cain, you will discover Wirt’s carcass near his usual hangout. When you click on it, a bunch of gold and several items will drop, as well as his peg leg, an important component of the Secret Cow Level.